A bomb was thrown from a moving car at a busload of U.S. troops and exploded Saturday, wounding three of the soldiers, the U.S. Embassy said.

Two bystanders also were wounded in the explosion, a local radio station reported.The attack occurred on one of the most crowded central streets of the city of Comayagua, 45 miles northeast of Tegucigalpa, the capital of Honduras.

The 28 soldiers were being driven to the U.S. military base at Palmerola.

The bomb was thrown from a moving car by an unidentified man, initial reports said. The bomb exploded in the back of the bus and blew out the windows, the reports said.

Two soldiers were taken to the military hospital at Palmerola and were released, while a third soldier remained hospitalized, but his condition was not immediately known, said embassy spokeswoman Ann Sigmund.

No one has claimed responsibility for the attack, Sigmund said.